With pinggy.io you can test your Shopify Webhook from localhost with just a single command. Replace the port 8080 with the port where your local development server is running and make sure it is ready to receive requests (e.g. http://localhost:3030/webhooks).
Pinggy will give you a URL like https://ranlkfsbjkxry.a.pinggy.link. Use this URL to access the webhook.